Dentifrice composition



United States Patent 3,105,798 DENTIFRIQE CUMPOSITION Wiiliain M. Holliday, Wyoming, Henry C. Schweizer, Sycamore Township, Hamilton County, and Paul E. Norris, Springfield Township, Hamilton County, Ohio, assignors to The Procter & Gamble Company, Cincinnati, Ohio, a corporation of Ohio No Drawing. Filed May 29, 1958, Ser. N 738,640 9 Claims. (Cl. 167-93) This invention relates to dentifrice compositions. More specifically it relates to improvements in dentifrices which contain stannous compounds and fluoride compounds.

A body of scientific literature shows that the use of toothpastes containing a source of stannous ions and fluoride ions reduces the rate at which dental caries are formed (I. C. Muhler et al., J. Dent. Res, 33, 606- (1954-); J. C. Muhler et al., J.A.D.A., 50, 1 63 (1955); J. C. Muhler et al., J. Dent. Res, 35, 49 (1956); W. A. Jordan et al., J.A.D.A., 54, 589* (1957)), and that the presence of stannous ions with fluoride ions gives a more effective paste than fluoride alone (I. C. Muhler et al., J.A.D.A., 51, 556 (1955)). However, a problem in the manufac ture and widespread distribution of such toothpastes is to maintain the stannous ions and fluoride ions, over a period of many months, in substantially as available a form for reduction of solubility of dental enamel as they are when the paste is fresh. Means have been provided for maintaining the fluoride ions in an available condition. However, to insure the maximum benefit to the user, the stannous ions must be available for reaction with the dental enamel and reduction of the solubility thereof. The stannous ions must not have been made unavailable to the dental enamel by oxidation to the stannic condition, hydrolysis to stannous hydroxide, or reaction with other constituents of the paste to form very stable complexes or highly insoluble compounds.

A copending application by Norris and Schweizer, Serial No. 647,956, filed March 25, 1957, now U.S. Patent 2,946,725, describes an advance in maintaining stannous tin in an available condition in a somewhat acidic toothpaste. The pH may be from 3.5 to 6.0 with the pH range of 4.0 to 5.5 being preferred. Higher pH values than 6 cause the stannous ions to react rapidly with other components of the paste and become non-available for reaction with dental enamel because of the insolubility of the reaction products. It is generally true that increas ing pH from about pH increases the rate, during storage of a toothpaste, at which stannous ions become non-available for reducing enamel solubility. Yet certain properties important to the consumer such as sudsing and taste of the toothpaste are improved as the pH is increased from about pH 5. Other properties such as texture can also be improved. Higher pH values than about pH 7 are often disadvantageous since certain flavoring ingredients, especially esters, may deteriorate rapidly. Thus the pH range of 6 to 7, which can make possible a favorable combination of properties important to the consumer, has not heretofore been available for use in formulating a highly effective dentifrice containing stannous and fluoride ions. Immediately below a pH of about 6 a compromise of maintaining stannous ions in an available condition vs. consumer properties must be made. Formulation of a dentifrice pleasant to the consumer is important in determining the commercial success of the dentifrice; it also affects the frequency at which the consumer will brush his teeth and thereby the state of his oral hygiene.

An almost insoluble stannous salt is used in Norris and Schweizer, US. Patent 2,946,725 to provide a reservoir of stannous ions. In association with water, at least 10 and not more than 1000 parts per million (p.p.m.) of

stannous ions are supplied from the solid reservoir. How- 3,105,798 Patented Oct. 1, 1963 ever, some of the solid must dissolve before additional stannous ions are available to the enamel, and no more than 1000 ppm. of stannous ions are provided by the reservoir at a given time.

It is advantageous to provide an excess of stannous ions as a reservoir and even more advantageous to pro vide the excess of stannous ions in a soluble, immediately usable, condition. Using stannous fluoride as the sole source of a high concentration of soluble stannous tin is not feasable. The stannous tin quickly becomes non-available for reaction with enamel as indicated above. Also, the two moles of fluoride carried along with each mole of stannous tin may cause the dentifrice to have toxic effects. Compounds such as stannous chlorofluoride introduce one mole of fluoride per mole of stannous tin, but the concentration of fluoride at the stannous tin concentrations required for an eflective reservoir is still high. Also, the problem of maintaining the stannous tin in a water-soluble, available condition is not solved. Combinations of stannous salts which do not contain fluoride (e.g. stannous chloride) and fluoride salts which are not stannous salts (e.g. sodium fluoride) permit the adjustment of stannous tin to fluoride ratios, but do not solve the problem of maintaining the stannous tin in a watersoluble, available condition.

An object of this invention is to provide a novel fluoridecontaining dentifrice in which the stannous ions are effectively maintained in an available condition for the reduction of the solubility of enamel.

A further object is to provide a dentifrice containing a high level of stannous tin in a Water-soluble condition for the reduction of the acid-solubility of enamel.

Another object is to provide a dentifrice containing a molar excess of stannous tin over fluoride, the stannous tin being maintained in a water-soluble, available condition.

Another object is to provide a dentifrice in which the stannous ions are maintained in an available condition at pH values of from 5 to 7, and especially in the pH range of from 6 to 7.

Another object is to provide a dentifrice in which the pH remains constant at the desired level.

Another object is to provide a dentifrice in which good consumer properties are attained without sacrifice of the availability of stannous ions for the reduction of enamel solubility.

Another object is to provide a dentifrice which is particularly effective in reducing the acid-solubility of enamel when it is applied in the presence of saliva.

Other objects and improvements will become apparent from the following specification.

In general this invention comprises a dentifrice containing a water-soluble fluoride, a source of aldonate groups containing six carbon atoms, capable of forming water-soluble complexes with stannous ions, and from about 5000 to about 15,000 ppm. of stannous tin in the form of water-soluble salts. The molar ratio of aldonate groups to stannous tin is from about one to about three. The molar ratio of stannous tin to fluoride is greater than one.

Stannous ions are maintained for long periods of time in the dentifrice in an unusually stable form available for the reduction of the acid-solubility of dental enamel. Furthermore, such availability of stannous ions is maintained at pH values of from about 5 to about 7, whereby a dentifrice more compatible with sudsing and flavor ingredients is provided.

The term aldonate group, as used herein, is intended to mean a group of atoms characteristic of an aldonate ion, except that the aldonate group need not be ionic; that is, it may be present as an aldonic acid, as a salt of an aldonic acid or aldonate, as complexes of a metal cation with aldonate ions, etc. Aldonic acids can be regarded as derived from sugars and have the empirical formula OHzOH They are discussed by W. W. Pigman and R. M. Goepp in Carbohydrate Chemistry (Academic Press Inc., New York, 1948); chapters '1 and VII are especially pertinent. The number of carbon atoms in compounds ordinarily considered as aldonic acids may vary from 3 to 7; but hereinafter the term aldonate group is intended to mean an aldonate group containing six carbon atoms. Like the sugars, they may belong to the D or the L-series according to the configuration of the asymmetric carbon atom farthest away from the COOi-I group in the chain. Aldonic acids quickly set up equilibria with lactones in aqueous solution. Hydroxyls in the gamma-position and in the delta-position can take part in the intermolecular elimination of a molecule of water required to form a lactone from an aldonic acid. An example of equilibria involving an aldonic acid containing six carbon atoms and gamma and delta lactones follows:

COOH

Aldonic acids can form water-soluble complexes with metallic cations and this ability is presumed to be essential to the present invention.

Many other compounds which form water-soluble com plexes with metallic ions are known, but the aldonates appear to be unique for the purposes of this invention. The complexing agent may be postulated to react with stannous ions to bind them tightly enough that their rate of becoming non-available to dental enamel by hydrolysis, oxidation, and precipitation is greatly reduced but not so tightly that they become non-available to dental enamel.

Examples of complexers which bind the stannous tons more tightly than aldonates, and which do not serve to achieve the objects of this invention, are pyr phosphate, triphosphate, ethylenediaminetetraacetate, and phytate. Examples of complexers which apparently do not bind the stannous ions tightly enough are lactate and salicylate.

The preferred aldonate group of this invention is the gluconate group. The term gluconate group is intended to mean a group of atoms characteristic of a gluconate ion, except that a gluconate group need not be ionic, that is, it may be present as a gluconic acid, as a water-soluble salt of a gluconic acid or a gluconate, as complexes of a metal cation with gluconate ions, etc. Gluconate groups may be supplied by any appropriate water-soluble compound. Examples of a preferred group of soluble compounds are stannous gluconate, sodium gluconate, potassium gluconate, gluconic acid, and glucono-lactone. In order to adjust the molar ratio of stannous tin to gluconate groups and the pH of the paste, it is often advantageous to use a mixture of more than one source of gluconate.

Sources of aldonates which will be suitable for this invention are the 6-carbon aldonates of the L and D-series in the form of their water-soluble salts, in the form of aldonic acids, and in the form of aldono-lactones. The six-carbon aldonate groups suitable for use in this invention are the D and L forms of gluconate, mannonate,

are of stannous ion leaves too much stannous tin uncomplexed, and the primary benefits of the aldonate are there by lost. More than about three moles of aldonate groups per mole of stannous tin is wasteful of material; and by the law of mass action, as applied to the complexation reaction involved, may reduce the concentration of tin available for reaction with enamel to an ineffective level. The ratio of aldonate groups to stannous tin can be adjusted, within the specified limits, to control the concentration of available tin. A desirable molar ratio of the preferred gluconate groups to stannous tin ions is in the range of from about twozone to threezone.

Preferred Water-soluble stannous salts for providing a source of stannous tin in the dentifrice of this invention are stannous fluoride, stannous aldonates, stannous chloride, and stannous sulfate. Mixed stannous halides such as Sn ClF and SnClF are also suitable. The total stannous tin content of the dentifrice can not be supplied solely by those salts having a molar ratio of stannous ions to fluoride ions of one or less. They are ordinarily used with a non-fluoride stannous salt such as a stannous aldonate.

The total stannous tin content must be from about 5000 to about 15,000 p.p.m., the preferred range being from about 6000 to about 10,500 p.p.m. stannous tin. Especially eifective dentifrices are obtained above a minimum total stannous tin content of 8000 p.p.m. The advantages of this invention are not substantially obtained below the lower limit; in the vicinity of the upper limit, treatment of enamel with increased concentration gives no further enamel solubility reduction. It is often preferred to add all or part of the stannous tin in the form frice is slurried with water, not all of the stannous tin is extracted into the water. Some has become less avail able by interaction with the abrasive, with the thickening agent, and with other ingredients of the toothpaste. The fraction of the total found in the water will depend on the ratio of Weight of dentifrice to volume of water, time of contact, age of the paste, etc. When soluble stannous tin is determined according to the procedure given in detail in Example III, freshly prepared pastes must provide a concentration, based on the toothpaste, in excess of about 2000 p.p.m. and preferably in excess of 4000 p.p.m. of soluble stannous tin.

If the fluoride is not added as a stannous salt, such as have already been named, sodium and potassium fluorides are preferred. Examples of other suitable fluoride salts include InF PdF FeF and UP and mixtures thereof. The term fluoride salts is also intended to include complex water-soluble fluoride-containing salts such as fiuosilicates, i.e., Na SiF fluozirconates, i.e., CaZrF Na ZrF K ZrF fiuostannites, i.e., KSnF fluoborates, i.e., NaBF and fluotitanatcs. fluoride salts can also be used.

The quantity of the water-soluble fluoride compounds which is used for efficacious results in the fluorine-com Mixtures of taining dentifrices of this invention should be an amount equivalent to at least 25 parts of fluoride ions per million parts of dentifrice. Extremely large amounts of fluoride ions do not appreciably enhance the desirable properties of the dentifrice and may cause it to have toxic effects. Accordingly, the dentifrices of this invention in general do not contain a total of more than 4000 parts ionized and un-ionized fluorine per million parts of dentifrice, and preferably not more than about 1000 parts per million. The molar ratio of stannous tin to fluoride is greater than onezone.

The pH of the dentifrice composition of this invention lies between about 5 and 7, the preferred range being from about 5.5 to 6.5. Above about pH 7 loss of stan: nous ions available for reaction with enamel can be too rapid; and, as has been mentioned before, certain flavoring substances, especially esters, deteriorate rapidly. Too low a pH, below about 5, in the dentifrice of this invention produces an astringent taste which is highly objectionable to most people. It also accelerates the hydrolysis of certain of the sudsing agents thereby producing an unpleasant fatty acid taste and reducing the amount of sudsing obtained in use. Furthermore, pH values below 5 tend to cause corrosion of metal tubes in which the paste is stored, and tend to hydrolyze other ingredients such as condensed phosphates if used as abrasives. Such hydrolysis can decrease the availability of stannous ions by providing anions with which they can form very stable complexes or with which they can precipitate as highly insoluble compounds. The pH values specified herein are for the supernatant from a slurry of one part dentifrice to three parts distilled water.

The pH of the dentifrice may be adjusted with strong acids such as HCl but it is particularly advantageous to use an aldonic acid or aldono-lactone. There is the economy of using one of the essential ingredients to serve a dual purpose; and to many persons the flavor of the dentifrice is improved, especially in the pH range up to about 5.5.

Dentifrices desirably should also contain abrasive rnaterials. The abrasives preferably should be relatively insoluble and relatively stable at the pH ranges herein specified. They desirably should not be too abrasive so as to scratch the surface of the teeth or unduly abrade the dentin, but they desirably should have just suflicient abrading power to clean the teeth. In the practice of this invention, any dental abrasives can be used which have these properties, and are sufficiently compatible with stannous ions and fluoride ions.

A preferred class of abrasives for use in fluoride containing dentifrices of this invention includes insoluble condensed phosphates. Examples of such insoluble con densed phosphates include calcium pyrophosphate, insoluble highly polymerized calcium polyphosphate sometimes called calcium polymetaphosphate, and insoluble highly polymerized sodium polyphosphatesometimes called insoluble sodium polymetaphosphate. Mixtures of abrasives can be used. The total amount of abrasive materials in dentifrices of this invention can range from 0.5% to 95% by weight of the dentifrice. Preferably, toothpastes contain from 20% to 60% by weight, and tooth powders contain from 60% to 95% by weight.

Dentifrices conventionally contain sudsing agents, although these are not critical in the practice of the present invention. Any of the commonly used sudsing agents can be used if they are reasonably stable and form suds Within the pH range of the dentifrices of this invention. Examples of suitable sudsing agents include, but are not limited to, water-soluble alkyl and alkyl ether sulfates and sulfonates having alkyl groups of from about 8 to 18 carbon atoms, water-soluble salts of sulfonated monoglycerides of fatty acids having from 10 to 18 carbon "solution.

atoms, water-soluble salts of sulfated fatty alcohols having from 10 to 18 carbon atoms, salts of fatty acid amides of taurines such as sodium-N-m-ethyl-N-palmitoyl tauride, salts of fatty acid esters of isethionic acid, and substantially saturated aliphatic acyl amides of saturated aliphatic monoaminocarboxylic acids having 2 to 6 carbon atoms and in which the acyl radical contains 12 to 16 carbon atoms, such as sodium N-lauroyl sarcoside. Mixtures of two or more sudsing agents can also be used.

Sudsing agents in an amount of from 0.5 to 5.0%, by weight of dentifrice, can be used in dentifrices of this invention.

In preparing toothpastes, it is necessary to add some thickening material. Preferred thickening agents are water-soluble salts of cellulose others such as sodium carboxym'ethyl cellulose and sodium carboxymethyl hydroxyethyl cellulose. Natural gums such as gum karaya, gum arabic, and gum tragacanth also can be used as thickeners, but may tend to cause undesirable odors or flavors in some formulations. Colloidal magnesium aluminum silicate or finely divided silica can be used as a part of the thickening agent for improvement in texture. Thickening agents in an amount of from 0.5% to 5.0% by weight of toothpaste, can be used to form a satisfactory toothpaste.

Suitable hunrectants include glycerine, sorbitol, and other polyhydric alcohols. The humectants may comprise up to about 35% of the toothpaste composition.

Dentifrices may additionally contain small amounts of fiavorings, such as oil of Wintergreen, oil of peppermint, oil of spearmint, oil of Sassafras, and oil of anise. Small amounts of sweetening agents such as saccharin, dextrose, levulose, and sodium cyclamate are also conventionally added to dentifrices.

If desired, a suitable food, drug and cosmetic-approved coloring agent may be added to the dentifrice.

The ability of a dentifrice to reduce the solubility of enamel in acid after teeth are treated with that dentifrice can be measured in laboratory tests; and, of course, the stability of the dentifrice on storage, with respect to supplying available stannous and fluoride ions to produce this solubility reduction, can be measured as a function of the age of the dentifrice; The tests are performed as follows:

Cleaned whole cuspidsland bicuspids are exposed to irradiation by neutron bombardment within the Oak Ridge National Laboratories graphite reactor. The teeth are irradiated in a'closed aluminum container containing a humid atmosphere to prevent their dehydration. The neutron flux is essentially constant throughout the mass of a tooth. Irradiation takes five days. A small part of the phosphorus and calcium throughout the calcium hydroxyapatite of the enamel is transformed to betaemitting P and Ca Immediately after exposure it is desirable to wait about a Week to permit the gammaemitting Na to decay; radiation from Ca is negligible at the time the teeth are used. Three radioactive teeth are mounted with plastic in the bottom of a large-diameter test tube. The plastic and all but the enamel of the teeth is then covered with an inert wax. The radioactive teeth are then etched by a measured volume of 0.1 N solution of lactic acid-sodium lactate which has been adjusted with NaOH to a pH of 4.5 at room temperature. The solution is stirred at constant speed and is maintained at a constant temperature of 37 C. by a water bath and thermostat. After 15 minutes duplicate samples of the solution are taken. A fresh portion of solution is used for each etching of the teeth; The amount of phosphorus and calcium etched from the teeth can be calculated by measuring the increase in radioactivity of the etching The radioactivity of samples of the solution is not measured directly; but they are placed in planchets, neutralized with sodium carbonate, and evaporated to dryness before counting with an end window Geiger tube "i and automatic scaler. The counts are corrected for coincidence loss. An initial etching is performed until the rate of etching of the tooth enamel becomes constant. The teeth are then etched for minutes and the amount of enamel removed is calculated from the measured radioactivity of the samples. A slurry is made containing 1 part of dentifrice thoroughly dispersed in 3 parts of water. This slurry is centrifuged, and the supernatant liquid is decanted. The teeth previously etched are immersed in ml. of this liquid for five minutes while the liquid is agitated. The teeth are then washed and exposed for 15 minutes to the etching solution in the same manner as before. The amount of enamel dissolved from the teeth is again determined, and the enamel solubility reduction, hereinafter referred to as ESR, is calculated as a percentage based on the amount of enamel dissolved from the teeth prior to treatment with the dentifrice. Since a result involves determinations on the same three teeth before and after trmtment, each set of teeth serves as its own control. The weight of enamel removed during a determination is small, and the area change during a test is negligible. Independent duplicate determinations are always made and their average is reported; each number reported is thus derived from six teeth.

To more closely approximate conditions in the human mouth, treatment can be carried out in the presence of saliva. The test is run as described above except that the dentifrice is slurried with a mixture of two par-ts saliva to one part water-instead of water alone. Thus the saliva can exert whatever effect it will on the active ingredients of the dentifrice or on their reaction with the enamel. The saliva is collected daily from several persons and stored in the refrigerator until use. Bacterial decomposition and person-to-person variations are thus minimized. This modification of the ESR test is hereinafter called the saliva ESR test, and results determined by its practice are called saliva ESR values.

The following examples illustrate this invention with greater particularity. Compositions are reported in weight percent. The stannous gluconate used in preparing the compositions of the examples was as supplied by Metal and Thermit Corporation. In reporting test results, a dash is intended to mean that no test was made after that time interval.

7 Example I The following toothpaste compositions containing 9000 ppm. stannous tin were prepared. After the indicated time intervals, BER and pH values were determined.

Sorbitol water) Saccharin Flavor Color Hydrochloric acid (3.7% solution) Stannous gluconate (A: 33.7% soln.;

stannous tluorid e Sodium fluoride... Glycerine Sodium coconut monoglyceride sulfonate Sodiumlauryl sulfate-.. Magnesium aluminum silicate- Sodium carboxymethyl cellulose Water Molar ratio gluconate groups to stannous n. Molar ratio stannous tin to fluoride After 1 week After 12 months..-

In composition A, where all of the stannous tin was furnished by stannous gluconate and fluoride was furnished by sodium fluoride, there was no decrease in stannous ions available for reduction of enamel solubility; the ESR value remained at a high level over an interval of a year of storage. The pH also did not change appreciably. Likewise, in composition B, where both stannous gluconate and stannous fluoride were employed, the ESR values remained at a high level; and the pH was substantially constant. saliva ESR value determined on a sample of composition A after 13 months of storage was 45.

Example II Example Ill The following toothpaste compositions containing 9000 ppm. of stannous tin in the form of water-soluble salts were prepared. After the intervals indicated, ESR, pH, and soluble stannous tin values were determined. Soluble stannous tin was determined by mixing one part toothpaste with three parts distilled water for 10 minutes. The solids were then separated by centrifugation for 20 minutes, at

15,000 rpm. and stannous ion concentration in an aliquot of the supernatant was determined iodometrically.

Results are reported as parts per million soluble stannous tin on the original paste basis.

Sorbltol (30% water) 20 .00 20 .00 Saccharin 0 .12 0 .12 Flavor 0.85 0 .85 Stannous gluconate (31.1% solution)- 12 .33 8 .22 Calcium pyrophosphate 40 .00 40 .00 Stannous fluoride. 0 .40 Sodium fluoride. 0.22 Glycerin 10 .00 10 .00 Sodium coconut monoglyce sulfonate- 0 .81 0 .81 Sodium lauryl sulfate 0 .70 0 .70 Magnesium aluminum silicate. 0 .40 0 .40 Sodium carboxymethyl cellulose. 1.15 1 .15 Water Balance Balance Molar ratio gluconate groups to stannous tin 2 .0 1 .3 Molar ratio stannous tin to fluoride. 1 .6 1 .5 pH (fresh) 6 .6 5 .3

Soluble Soluble ESR Sn, ESR Sn,

p.p.m ppm.

After 1 Week.-. 43 47 After 2 weeks 6, 880 4, 310 After 4 Weeks. After 6 Weeks After 8 weeks- After 12 weeks.

Both toothpastes maintained high ESR values on storage; the pH of each remained essentially constant. The soluble stannous tin values show that appreciable fractions of the total tin are initially available and remain available after 12 weeks storage. In conventional tooth brushing use, these toothpastes were judged to have excellent flavor characteristics, superior to those of a stannous fluoride dentifrice having a pH slightly below 5. Their sudsing characteristics were equal to those of a highly successful conventional slightly alkaline dentifrice and superior to the stannous fluoride dentifrice. The texture and viscosity of these toothpastes were good.

Example IV The following toothpaste compositions further illustrate the invention.

The saliva ESR was 40 after- Sorbitol (30% water) n 20 .00 20.00 Sac harm 0.12 .12 Flavor 0.85 0.85 Color. 0 .47 0 .47 stannous glueonate (31.6% soln.) 5.00 8 .10 Calcium pyrophosphate 40 .00 40 .00 Stannous fluoride 0 A0 Sodium fluoride 0.19 Glycerin 10 .00 10 .00 Sodium coconut monoglyceride sulfonate 0.81 0.81 Sodium lauryl sulfate 0 .70 0 .70 Magnesium aluminum silicate 0 .40 0 .40 Sodium carboxymethyl cellulose 1 .10 1 .10 Water Balance Balance Molar ratio, stannous tin to fluoride 1.1 1 .1 Molar ratio gluconate groups to stannous t 1.1 2 .0 Total stannous tin, ppm 6720 6000 These compositions maintain stannous tin in .an available condition for the reduction of solubility of enamel. A substantially constant pH of about 5.5 is maintained in A and of about 7.0 to 6.5 in B. The toothpastes have good consumer properties and are compatible with sudsing and flavor ingredients.

Example V The following toothpaste composition containing 9000 p.p.m. stannous tin and adjusted to the desired pH with D-glucono-delta-lactone was prepared. ESR values were measured in saliva, and pH values were determined after the indicated time intervals.

Sorbitol (70% soln.) 20.00 Saccharin 0.12 Flavor 0.85

Color 0.47 tannous gluconate (32.2% soln.) 8.04 D-gluccno-delta-lactone 0.20 Calcium pyrophospha-te 40.00 Stannous fluoride 0.40 Glycerin 10.00 Sodium coconut monoglyceride sulfonate 0.81 Sodium lauryl sulfate 0.70 Magnesium aluminum silicate 0.40 Sodium carboxymethyl cellulose 1.20 Water Balance Molar ratio gluconate groups to stannous tin 1.5 Molar ratio stannous tin to fluoride 1.5 Saliva ESR After 0 Week 46 After 4 months 42 This paste had good consumer properties. The pH remained substantially constant at about 5 and the availability of stannous ions for reduction of the solubility of enamel remained high during storage.

Example VI A toothpaste having the composition of Example I-A except that stannous galactonate is substituted for stannous gluconate exemplifies the invention. The composition maintains stannous tin in an available condition for reduction of enamel solubility, maintains a fairly constant pH of about 5.3 and is compatible with sudsing and flavor ingredients.

What is claimed is:

1. A dentifrice composition having incorporated therein an enamel solubility reducing material consisting essentially of:

(1) a Water-soluble fluoride salt providing at least 25 parts of fluoride ions per million parts of dentifrice, the total amount of ionized and unionized fluorine not exceeding 4000 parts per million parts of dentifrice,

(2) stannous tin in the form of a Water-soluble salt, providing a total content of stannous tin in solution of from about 5000 to about 15,000 parts per million parts of dentifrice, and

(3) a water-soluble source of six-carbon aldonate groups capable of forming water-soluble chemical complexes with stannous tin, the molar ratio of aldonate groups to stannous tin being in the range of from about onezone to about threezone, the molar ratio of stannous tin to fluoride ions being greater than onezone, said dentifrice having a pH of from about 5 to 7.

2. The dentifrice composition of claim 1 wherein the source of al'donate groups is a stannous aldonate.

3. The dentifrice composition of claim 1 wherein the source of aldonate groups is a sodium aldonate.

4. The dentifrice composition of claim 1 wherein the aldonate is a member selected from the group consisting of g-luconate and galactonate groups and mixtures thereof.

5. The dentifrice composition of claim 1 wherein the stannous tin salt is a member selected from the group consisting of stannous fluoride, stannous chloride, stannous sulfate, stannous aldonates containing six carbon atoms, and mixtures thereof and the source of at least part of the stannous tin and aldonate groups is a stannous aldonate containing six carbon atoms.

6. A toothpaste having incorporated therein an enamel solubility reducing material consisting essentially of a quantity of a water-soluble fluoride salt and stannous gluconate sufficient to provide from about 6000 to about 10,500 parts of stannous tin and at least 25 parts of fluoride ions per million parts of toothpaste but not more than about 4000 parts total of ionized and un-ionized fluorine per million parts of toothpaste, and a molar ratio of gluconate to stannous tin in the range of from about onezone to about three:one and a molar ratio of stannous tin to fluoride greater than onezone, said toothpaste having a pH of from about 5.0 to 7.0.

7. The toothpaste of claim 6 wherein the Water-soluble fluoride salt is stannous fluoride.

8. The toothpaste of claim 6 wherein the water-soluble fluoride salt is sodium fluoride.

9. A toothpaste having incorporated therein an enamel solubility reducing material consisting essentially of a quantity of stannous fluoride and sodium gluconate suflicient to provide from about 6000 to about 10,500 parts of stannous tin and at least 25 parts of fluoride ions per million parts of toothpaste, but not more than about 4000 parts total of ionized and un-ionized fluorine, and a molar ratio of gluconate to stannous tin in the range from about one:one to about threezone and a molar ratio of stannous tin to fluoride greater than about onezone, said toothpaste having a pl-T in the range from about 5.0 to 7.0.

References Cited in the file of this patent I UNITED STATES PATENTS 1,893,872 Schmidt et al. Jan. 10, 1933 2,215,429 Schmidt et al Sept. 17, 1940 2,236,970 Goldfarb Apr. 1, 1941. 2,749,278 Moss June 5, 1956 2,772,203 Salzmann Nov. 27, 1956 2,818,371 Wessinger Dec. 31, 1957 2,946,725 Norris July 26, 1960 FOREIGN PATENTS 644,360 Great Britain Oct. 11, 1950 654,473 Great Britain June 20, 1951 746,550 Great Britain Mar. 14, 1956 OTHER REFERENCES Bergy: Amer. 1. Pharmacy, June 1954 (pp. 208-209 pert).

Muhler et al.: J.A.D.A., vol. 41, November 1950, pp. 528-535.

Walsh: Reduction in the 'Acid Solubility of Dental Enamel by Fluoride Solutions and Fluoride-Containing Dentifrices, Dept. of Chemistry, Indiana U., September 1953, 91pp. (pp. 34, 40-42, and 51 pert).

Pigman et al.: Chemistry of the Carbohydrates, Academic Press Inc., New York (1948), pp. 93, 96, and 290. 

1. A DENTIFRICE COMPOSITION HAVING INCORPORATED THREIN AN ENAMEL SOLUBILITY REDUCING MATERIAL CONSISTING ESSENTIALLY OF: (1) A WATER-SOLUBLE FLUORIDE SALT PROVIDING AT LEAST 25 PARTS OF FLUOORIDE IONS PER MILLION PARTS OF DENTIFRICE, THE TOTAL AMOUNT OF IONIZED AND UNIONIZED FLUORINE NOT EXCEEDING 4000 PARTS PER MILLION PARTS PER MILLION FRICE, (2) STANNOUS TIN IN THE FORM OF A WATER-SOLUBLE SALT, PROVIDING A TOTAL CONTENT OF STANNOUS TIN IN SOLUTION OF FROM ABOUT 5000 TO ABOUT 15,000 PARTS PER MILLION PARTS OF IDENTIFRICE, AND (3) A WATER-SOLUBLE SOURCE OF SIX-CARBON ADONATE GROUPS CAPABLE OF FORMING WATER-SOLUBLE CHEMICAL COMPEXES WITH STANNOUS TIN, THE MOLAR RATIO OF ALDONATE GROUPS TO STANNOUS TIN BEING IN THE RANGE OF FROM ABOUT ONE:ONE TO ABOUT THREE:ONE, THE MOLAR RATIO OF STANNOUS TIN TO FLUORIDE IONS BEING GREATER THAN ONE:ONE: SAID DENTIFRICE HAVING A PH OF FROM ABOUT 5 TO
 7. 